Bipolar transistor

Abstract

A bipolar transistor having base and collector regions of narrow bandgap semiconductor material and a minority-carrier excluding base contact has a base doping level greater than 10 17 cm −3 . The transistor has a greater dynamic range, greater AC voltage and power gain-bandwidth products and a lower base access resistance than prior art narrow band-gap bipolar transistors.

What is claimed is:  
     
       1. A bipolar transistor having emitter and collector regions arranged to extract minority carriers from the base region, a structure for counteracting entry of minority carriers into the base region via the base contact, the base region having a band gap less than 0.5 eV and wherein the base region has a doping level greater than 10 17  cm −3 . 
     
     
       2. A bipolar transistor according to  claim 1  wherein the base region has a doping level greater than that of the emitter region, and where the emitter region has a wider bandgap than that of the base region. 
     
     
       3. A bipolar transistor according to  claim 1  wherein the structure for preventing entry of minority carriers into the base via the base contact is an excluding heterostructure. 
     
     
       4. A bipolar transistor according to  claim 1  wherein the structure for counteracting entry of minority carriers into the base via the base contact is an implanted region within the base region, making the doping level of the base contact higher than that of the base itself. 
     
     
       5. A bipolar transistor according to  claim 4  wherein the transistor includes an integral passivation layer between the base and emitter regions, using the wide gap emitter region externally to the emitter, and having its doping type converted to that of the base using the base contact implant.